Studies will be carried out to determine basis mechanisms of cell adhesion and the role of fibronectin in adhesion in vitro and in vivo. Experiments are planned in the following areas. (1) Cell surface and cytoskeletal components that become associated with fibronectin coated latex beads will be determined using immunological and biochemical methods after initial bead binding to the cells and after phagocytosis. (2) Binding of soluble fibronectin to cells at 4 degrees will be studied to determine dependence on time, cell concentration, fibronectin concentration and binding specificity. Topographical distribution and bound fibronectin turnover will also be determined. (3) Phenotypic characteristics of baby hamster kidney adhesion variants will be analyzed to determine interactions with fibronectin or lectin coated beads or culture dishes. (4) The in vivo distribution of fibronectin in relationship to connective tissue organization will be studied during blastocyst implantation and trophoblast invasion in the rat. These studies will utilize indirect immunofluorescence analysis of frozen thick sections.